Self-cleaning intake screens are well known in the art. The earliest of such devices simply employed some mechanism to cause the screen, generally cylindrical in shape, to rotate within the stream or waterway. As the screen rotated, any debris trapped on its upstream side would be washed away as it turned downstream. More sophisticated devices employ some sort of backwash system which, either continually or at periodic intervals, spray a high pressure jet of water or air against the inside of the screen in an attempt to blow debris off of and away from the screen. However, most self-cleaning intake screen designs are complicated and/or do not effectively keep the screen free from debris.
Further, for many applications of intake screens, there is a maximum flow rate per unit area of screen that cannot be exceeded in order to protect fish and other wild life that are in the water passing through the intake screen. Simply making the screen larger to reduce the per unit area flow rate is ineffective since the water tends to flow through the central portion of the screen.
There is a need for an intake screen that reliably and effectively cleans itself, as well as minimizes the maximum water flow rate passing through the screen.